Disk drives for storing electronic information are found in a wide variety of computer systems, including workstations, personal computers, and laptop and notebook computers. Such disk drives can be stand-alone units that are connected to a computer system by cable, or they can be internal units that occupy a slot, or bay, in the computer system. Laptop and notebook computers have relatively small bays in which to mount internal disk drives and other peripheral devices, as compared to the much larger bays available in most workstation and personal computer housings. The relatively small size of peripheral bays found in laptop and notebook computers, can place significant constraints on the designer of internal disk drives for use in such computers. Techniques that address and overcome the problems associated with these size constraints are therefore important.
Disk drives of the type that accept removable disk cartridges have become increasingly popular. One disk drive product that has been very successful is the ZIP.TM. drive designed and manufactured by Iomega Corporation, the assignee of the present invention. ZIP.TM. drives accept removable disk cartridges that contain a flexible magnetic storage medium upon which information can be written and read. The disk-shaped storage medium is mounted on a hub that rotates freely within the cartridge. A spindle motor within the ZIP.TM. drive engages the cartridge hub when the cartridge is inserted into the drive in order to rotate the storage medium at relatively high speeds. A shutter on the front edge of the cartridge is moved to the side during insertion into the drive, thereby exposing an opening through which the read/write heads of the drive move to access the recording surfaces of the rotating storage medium. The shutter covers the head access opening when the cartridge is outside of the drive, to prevent dust and other contaminants from entering the cartridge and settling on the recording surfaces of the storage medium.
The ZIP.TM. drive is presently available for workstations and personal computers in both stand-alone and internal configurations. In order to provide a version of the ZIP.TM. drive for use in laptop and notebook computers, the size constraints of the peripheral bays of such computers must be considered. In particular, for an internal drive to fit in the majority of laptop and notebook peripheral bays, the drive must be no longer than 135 mm. The height of the drive must be in the range of 12 to 15 mm. These dimensions place many constraints on the design of such a drive, and give rise to numerous design problems.
Additional features of an exemplary drive in which the present invention can be employed is demonstrated in commonly assigned applications: Ser. No. 08/866,189, filed on May 30, 1997, entitled "An Improved Operating System For Operating An Eject System And A Head Retraction System Of A Disk Drive"; Ser. No. 08/866,225, filed on May 30, 1997, entitled "An Improved Head Retraction System for Retracting The Heads Of A Disk Drive"; Ser. No. 08/866,177, filed on May 30, 1997, entitled "Motor Loading System For A Disk Drive"; and Ser. No. 08/866,226, filed on May 30, 1997, entitled "An Improved Eject System For Ejecting A Disk Cartridge From A Disk Drive", all of which are hereby incorporated herein by reference in their entirety.
Disk drives often employ linear actuators for positioning read/write heads of the disk drive over the surfaces of the storage media. Actuator carriage assemblies are used to carry the heads for magnetic disk drives, CD players, and optical drive devices. Magnetic flux for the actuator carriage assembly is typically generated by a magnetic circuit comprising a return path assembly, a pair of magnets, and a voice coil.
Typically, a single-loop flex circuit is attached to the actuator carriage assembly to (1) supply current to the voice coil and (2) carry signals between the heads and an electric circuit board. One drawback of a single-loop flex circuit is that it is unnecessarily wide because it carries both the current supplied to the coil and the signals to and from the read/write heads on the same loop. Thus, it is desirable to provide a flex circuit for an actuator carriage assembly that does not require as much space as a single-loop flex circuit.
A common problem with carriage assemblies utilizing single-loop flex circuits is that the signals carried to and from the read/write heads are subject to electrical or induced noise from the line of current supplied to the coil. The relatively large amount of current supplied to the voice coil creates a magnetic field around the wire carrying the current, resulting in induced noise that interferes with the relatively small electrical signals to and from the read/write heads. Because the current supplied to the coil and the signals to and from the heads are adjacent to each other in a single loop flex circuit, induced noise is a substantial problem. Thus, it is desirable to provide a flex circuit for an actuator carriage assembly that minimizes the induced noise that the line of current supplied to the coil imparts on the signals to and from the read/write heads.
A co-pending application having Ser. No. 08/728,128, entitled, "Actuator For Data Storage Device," hereby incorporated herein by reference in its entirety, describes an actuator carriage assembly having a central guide track (or center rod) on which bushings within the actuator carriage assembly ride. Each of the bushings, actuator carriage assembly arm assemblies, and coil are spaced substantially symmetrically about the center rod. Such symmetrical spacing is an advantage because it aligns the carriage center of mass and center of force along the center rod. Such alignment minimizes friction and avoids binding forces and resonance problems.
Although the center rod linearly directs the actuator carriage assembly, the actuator carriage assembly remains unrestrained from rotating axially around the center rod. Such rotation causes the carriage to roll about the center axis, i.e., the axis through which the center rod is centered. This roll of the carriage, in turn, adversely affects the accurate pitch of the read/write heads, i.e., from the perspective of the heads as they face 90.degree. from the axis of the center rod to the rotating storage media as it rotates toward the heads. This roll of the carriage can also cause the voice coil to make contact with the cover of the actuator carriage assembly which is located directly above the voice coil at a very close distance, typically 0.25 mm or less.
A drawback of a single-loop flex circuit is that it gives the actuator carriage assembly a tendency to roll. The attachment of a flex circuit to the side of the actuator carriage assembly imparts a force on the assembly, tending to bind the assembly as the carriage moves along the center rod. As the carriage moves back and forth, the flexibility of the flex circuit imparts a moment force on the actuator carriage assembly that gives the assembly a tendency to roll about the center axis. Thus, it is desirable to provide a flex circuit for an actuator carriage assembly that does not result in affecting the roll of the actuator carriage assembly.